1. Field of the Invention
The present invention relates to photographic silver halide emulsions stabilized against latent image fading and to photographic elements including such emulsions especially for use in color photography.
2. Description of the Prior Art
It is known in the art that obtaining of photographic images by exposure and development of a photographic element may be negatively effected by fading of the latent image. It has been described in U.S. Pat. No. 3,954,478 that certain benzothiazolium salt compounds, previously known in the art as antifoggants (see German Pat. No. 867,355) are particularly useful as latent image stabilizers. It has been described in U.S. Pat. No. 4,423,140 that certain compounds, which are obtained by alkaline hydrolysis of said compounds, are more effective than the benzothiazolium salt compounds of U.S. Pat. No. 3,954,478. It has been described in U.S. Pat. No. 4,374,196 that the hydrolysis products of certain thiazolium salt compounds are active as latent image stabilizers, while the salt compounds are not.
All of the benzothiazolium and thiazolium salt compounds and their hydrolysis products described in such patents as latent image stabilizers include an N-alkenyl substituent (described for the first time in German Patent 867,355), which appear to be sufficient to impart latent image stabilizing properties to the benzothiazolium salt compounds but not to the thiazolium salt compounds.